Limit control



July 17, 1951 H. E. HODGSON ETAL LIMIT CONTROL Filed Sept. 5, 1947 Patented July 17, 1951 LIMIT CONTROL Howard E. Hodgson, Wauwatosa, and Richard R.

Ranson, Whitefish Bay, Wis., assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application September 5, 1947, Serial No. 772,444

' vide a limit switch driving mechanism which enables limit switches of various types having a relatively short operating range to be used in the control of apparatus such as motor driven sluice gates which require an exceedingly long range of travel and exceedingly accurate control within short zones at opposite ends of such range.

Another object is to provide a limit switch driving mechanism for the aforesaid purpose which operates to drive an associated limit switch during travel of the gate through predetermined parts of its range and to positively lock the same against operation during travel of the gate through the remainder of its range.

Another object is to provide a limit switch operating mechanism of the aforesaid type which is simple and rugged in construction. positive and reliable in operation and which operates to insure exact registry of the limit switch with respect to the gate operating mechanism at all times.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawin illustrates an embodiment of the invention which will now be described; it being understood that the embodiment illustrated is susceptible of modification without departin from the spirit and scope of the appended claims.

In the drawing,

Figure 1 diagrammatically illustrates a motor operated sluice gate having a limit switch driving mechanism embodying the invention associated therewith;

Fig. 2 is a schematic view of the limit switch driving mechanism illustrated generally in Fig. 1, and

Fig. 3 is a sectional view on line 3-3 of Fig. 2.

Referring to Fig. 1, the same illustrates a sluice gate l and a driving motor 2 therefor, which is shown as being operatively connected to said gate through the medium of a conventional gear drive comprising a driving pinion 3 and associated rack I which is fixed to said gate. It is assumed that the gate has a' long range of travel, as for example 125 it, between closed and raised limits marked CL and RL and that the same must be accurately controlled within a zone Z at the lower end of said range which may ex- 2 tend for a distance of 20 ft. and within a zone Z at the upper end of said range which may extend for a distance of 5 ft. The control means for motor 2 includes a limit switch Ls which may be of the traveling nut type and may be provided with various control contacts for effecting slowdown and stopping of the motor during movement of gate I into its raised and closed limits. In accordance with the present invention the operating screw 5 of limit switch LS is operatively connected to gate I through the medium of a driving mechanism 6 which operates as hereinafter set forth to drive said screw during movement of the gate in zones Z and Z and to lock said screw against operation during movement of the gate through the remainder of its range.

As shown in Fig. 2, driving mechanism 6 includes a drive shaft 1 and a driven shaft 8, the former being driven from gate I by suitable means, as for example a pinion 9 which meshes with rack 4, and the latter bein coupled to the operating screw 5 of limit switch LS. Said driving mechanism also includes a releasable coupling III for connecting drive shaft 1 to driven shaft 8, a circular cam element II for effecting release and engagement of said coupling and an intermittent gear drive l2 between said cam element and drive shaft 1 for operating said cam element to effect engagement of said coupling during movement of gate l in zones Z and Z and to effect release of said coupling during movement of said gate through the remainder of its operating range.

More specifically, coupling Ill comprises a pair of flanges l3 and H, the former being fixed to drive shaft 1 and the latter being keyed to driven shaft 8 to rotate therewith and to permit axial movement thereon. Flange 14 carries a pair of pins l5 and upon movement of said flange toward the left out of the position shown in Fig. 2 said pins engage within openings IS in flange l3 to couple drive shaft I to driven shaft 8. Flange l4 also carries pins I! which engage within openings ill in fixed stops I!) to lock driven shaft 8 against rotation when said flange is moved into the position shown in Fig. 2. Flange I4 is operatively connected to cam element ll by a shifter element 20 which is pivotally mounted upon a stationary pin 2|. Said shifter element is provided with operating rollers 22 and 23 for engaging opposite sides of flange l4 and the same is also provided with rollers 24 and 25 for engagement with opposite sides of cam element ll.

Cam element II is rotatably mounted upon drive shaft 1 and is provided with two cam segdisengaged position shown in Fig. 2. Cam segment 21 is arranged between the end faces of cam segment 28 and as shown in Fig. 3 the same extends through an angle of substantially 72 deg. Cam segment 21 is provided with radially disposed beveled end faces 21*, 21 which cooperate with roller 25 to operate shifter element 29 for movement of flange it into engaged position.

As shown in Fig. 2, the intermittent gear drive between cam element H and drive shaft 1 comprises three intermittent gear sets A, B and C, each consisting of a gear wheel 29, an operating arm 99 and a locking disk 9|. Each of the gear wheels 29 is provided with five equally spaced radial slots 92 and is further provided with concave circular faces 99 which extend between said slots. Each of the arms 99 is rotatably supported at one end and has an operating pin 94 mounted upon its free end which momentarily engages within one of the slots 92 of its associated gear wheel during each revolution of said arm to effect quick rotation of said gear wheel through one-fifth of one complete revolution. Each of the locking disks 9| is fixed to its associated arm 99 to rotate therewith and is provided with a circular surface 96 for engaging the surfaces 99 on its associated gear wheel 29 to lock the latter against rotation immediately after the same is operated by its associated pin 94.

Gear wheel 29', arm 90'' and gear wheel 29 of gear sets A, B and C are rotatably mounted upon drive shaft I and arm 99", gear wheel 29 and arm 99 of said gear sets are rotatably mounted upon a fixed supporting shaft 99. Arm 99 is fixed to a gear 99 which is rotatably mounted upon shaft 99 and is driven from drive shaft 1 by a gear 49. Arm 9!!' is fixed to gear wheel 29* to rotate therewith and is disposed in radial alinement with one of the slots thereof, and arm 90 is fixed to gear wheel 29" to rotate therewith and is also disposed in radial alinement with one of the slots thereof. Gear wheel 29 is fixed to cam element H in the angular position shown in Fig. 3 so that roller 25 is located midway between the end surfaces 21 and 21 of cam segment 21 when said gear wheel is locked by its associated disk 9l in the angular position shown in this figure.

As is apparent, when arm 99' of the aforedescribed intermittent gear drive I2 is rotated in either direction gear wheel 29 is quickly stepped ahead one-fifth of one revolution each time said arm completes 25 revolutions so that cam element II is maintained in each of five equally spaced operating positions during substantially 25 revolutions of arm 99. Fig. 3 illustrates cam element II in one of its operating positions and when the same is rotated in either direction out of such position, cam segment 26 engages roller 24 to move coupling flange ll into the disengaged position shown in Fig. 2. Upon return of cam element II in either direction into the operating position shown in Fig. 3, cam segment 21 engages roller 25 to move coupling flange ll into its engaged position. As is apparent, cam segment 26 operates to maintain coupling flange ll in disengaged position during substantially 100 revolutions of arm 99 and cam segment 21 operates when moved in either direction into the operating position shown in Fig. 3 to maintain said coupling flange in engaged position during substantially 25 revolutions of said arm. It should be noted that arms 99 of the several gear sets are of such length that the angular speed of arm 99 with respect to arm 99 is multiplied at the moment said arms move through the angular positions shown in Fig. 2. Also it should be noted that the beveled end faces a and b of cam segments 26 and 21 operate to effect substantially instantaneous movement of coupling flange it between its engaged and disengaged positions at moments when said arms are moving in one direction or the other through the angular positions shown in Fig. 2. Gears 99 and 49 may be of various ratios, as for example a 1 to 1 ratio which provides for one step of operation of cam element ii for 25 complete revolutions of drive shaft 1, and coupling flange I9 is angularly positioned on said drive shaft so that its openings ii are alined with the openings II in stops is at the moment coupling flange II is shifted into its engaged or disengaged position.

Assuming that drive shaft 1 is operatively connected to gate I so that the same makes one complete revolution for each foot of travel of the gate and that gears 99 and 40 have a 1 to 1 ratio. Also assume that the intermittent gear drive I2 is set with respect to gate I so that at the moment said gate moves into the upper and of closing zone Z cam segment 29 engages its associated roller 24 to move coupling flange it into its disengaged position. As is apparent from the foregoing, cam segment 29 then operates to maintain coupling flange I in disengaged position for disconnection of limit switch LS from drive shaft I during 100 ft. of travel of the gate in either direction between the lower and upper zones Z and 2. However, when gate i is moved upwardly into zone Z or downwardly into zone-Z cam segment 21 operates to move coupling flange ll into its engaged position for operation of limit switch L8 in these zones. As is apparent, limit switch 1.8 may be adjusted to eifect stopping of motor M upon 20 ft. of downward travel of the gate in zone Z and upon 5 ft. of upward travel of the gate in zone Z The above described driving mechanism may be mounted within a suitable casing to provide a separate unit as shown in Fig. 1, or if desired the same may be embodied with the limit switch mechanism to provide a single unitary structure.

What we claim as new and desire to secure by Letters Patent is:

1. The combination with a motor driven device having a long operating range and a control device therefor having a relatively short operating range, of a rotatable drive shaft for said control device operable by said driven device during movement thereof throughout its entire operating range, a releasable coupling for connecting said control device to said drive shaft, and control means for said coupling including an intermittent gear operating connection between the same and said drive shaft for maintaining said coupling in disengaged position during movement of said driven device through a major part of its operating range and for engaging the same during movement of said driven device through the remainder of its operating range.

2. The combination with a reversible motor driven device having a long operating range and a control device therefor having a relatively short operating range, of a rotatable drive shaft for said control device operable by said driven device during movement thereof throughout its entire operating range, a releasable coupling for connecting said control device to said drive shaft, and means for controlling said coupling to effect engagement thereof during movement of said driven device within predetermined short zones at opposite ends of its operating range and for effecting disengagement thereof during movement of said driven device between said zones, said means including an intermittent gear operating connection between said coupling and said drive shaft.

3. The combination with a reversible motor driven device having a long operating range and a control device therefor having a relatively short operating range, of a rotatable drive shaft for said control device operable by said driven device during movement thereof throughout its entire operating range, a releasable coupling for connecting said control device to said drive shaft, and means for controlling said coupling to effect engagement thereof during movement of said driven device within predetermined short zones at opposite ends of its operating range and for effecting disengagement thereof during movement of said driven device between said zones, said control means including a rotatable cam element for effecting release and engagement of said coupling, and an intermittent gear operating connection between said cam element and said drive shaft.

4. The combination with a reversible motor driven device having a long operating range and a control device therefor having a relatively short operating range, of a rotatable drive shaft for said control device operable by said driven device, during movement thereof throughout its entire operating range, a releasable coupling for connecting said control device to said drive shaft, means associated with said coupling for positively locking said control device against operation upon release of said coupling, and means for controlling said coupling to effect engagement thereof during movement of said driven device within predetermined short zones at opposite ends of its operating range and for effecting disengagement thereof during movement of said driven device between said zones, said means including an intermittent gear operating connection between said coupling and said drive shaft,

5. The combination with a control device having a short operating range, of a drive shaft therefor having a relatively long operating range, a releasable coupling for connecting said device to said shaft, an operating connection between said coupling and said shaft including an intermittent gear drive, and means controllable by said intermittent gear drive for effecting release and engagement of said coupling, said coupling being operatively connected at all times to said shaft through the medium of said intermittent gear drive, and said intermittent gear drive acting to maintain said coupling in released position during movement of said shaft throughout a major part of its operating range and then effecting engagement of said coupling throughout the remainder of the operating range of said shaft.

6. The combination with a control device having a short operating range, of a drive shaft therefor having a relatively long operating range, a releasable coupling for connecting said device to said shaft, a cam element for effecting release and engagement of said coupling, andan intermittent gear drive between said cam element and said shaft, said cam element being operatively connected at all times to said shaft through the medium of said intermittent gear drive, and said intermittent gear drive per se acting to control said cam element to effect engagement of said coupling during movement of said drive shaft within predetermined short zones of opposite ends of its operating range and to effect disengagement of said coupling during movement of said drive shaft between said zones.

7. The combination with a reversible motor driven device having a long operating range, a limit switch for stopping said motor driven device at opposite ends of its range, said limit switch having a relatively short operating range, of a rotatable drive shaft for said limit switch operable by said driven device during movement thereof throughout its entire operating range, a releasable coupling for connecting said limit switch to said drive shaft and an operating connection between said coupling and said drive shaft including an intermittent gear drive, and means controllabl by said intermittent gear drive for effecting engagement and disengagement of said coupling, said coupling being operatively connected at all times to said shaft through the medium of said intermittent gear drive, and said intermittent gear drive acting to effect engagement of said coupling during movement of said driven device within predetermined short zones at opposite ends of its operating range and to effect disengagement of said coupling during movement of said driven device between said zones.

8. The combination with a movable element having a long range of movement, of a limit switch therefor having a relatively short range of movement, a rotatable drive shaft for said limit switch operable by said movable element during movement thereof throughout its entire range, a releasable coupling for connecting said switch to said drive shaft, and means for controlling said coupling to effect engagement thereof during movement of said movable element within predetermined short zones within its operating range and for effecting disengagement thereof during movement of said element between said zones, said means including an intermittent gear operating connection between said coupling and said drive shaft.

9. The combination with a movable element having a long operating range, of a limit switch therefor having a relatively short operating range, a rotatable drive shaft for said limit switch operable by said movable element during movement thereof throughout its entire operating range, a releasable coupling for connecting said switch to said shaft, and means for controlling said coupling to effect engagement thereof during movement of said movable element within predetermined short zones within its operating range and for effecting disengagement thereof during movement of said movable element between said Zones, said control means including a rotatable cam element for effecting release and engagement of said coupling, and an intermittent gear operating connection between said cam element and said drive shaft.

10. The combination with a movable element having a long operating range and a limit switch therefor having a relatively short operating range, of a rotatable drive shaft for said limit switch operable by said movable element during nection between said cam element and Oak! drive shaft.

HOWARD E. uonason. RICHARD R. RANSON.

REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 275,008 A Wyman Apr. 3, 1883 1,042,905 Gamble Oct. 29, 1912 

